Lettuce grown in zero gravity is more susceptible in space to bacterial infections such as E. coli and Salmonella than on Earth, according to new research from the University of Delaware.
Published this week in the journals Scientific Reports and npj Microgravity, the research reveals that lettuce grown under conditions that imitate the weightless environment aboard the International Space Station is more susceptible to infection by human pathogens.
Space Salad
Lettuce has been grown in hydroponic chambers on the ISS for over three years and is regularly used to improve astronauts’ diets of flour tortillas and powdered coffee. However, researchers are concerned that foodborne illness outbreaks aboard the ISS—which is home to disease-causing pathogenic bacteria and fungi—could derail a mission.
University of Delaware researchers grew lettuce under conditions that imitate the weightless environment aboard the ISS, partly by rotating plants at the speed of a rotisserie chicken. The researchers found that the tiny pores in leaves and stems that plants use to breathe, called stomata, normally close to defend a plant when it senses a stressor, like bacteria, nearby.
Open To Attack
However, when the researchers added bacteria to lettuce under their microgravity simulation, they found the leafy greens opened their stomata wide instead of closing them. “The fact that they [lettuce plants] were remaining open when we were presenting them with what would appear to be a stress was really unexpected,” said Noah Totsline, an alumnus of the University of Deleware’s Department of Plant and Soil Sciences and the lead author of both papers.
Ultimately the researchers discovered that Salmonella can invade leaf tissue more easily under simulated microgravity conditions than it can under typical conditions on Earth.
Be Prepared
“We need to be prepared for and reduce risks in space for those living now on the International Space Station and for those who might live there in the future,” said Kali Kniel, a professor in microbial food safety at the University of Delaware’s Delaware Biotechnology Institute. “We need to better understand the interactions between human pathogens on plants grown in space.”
It’s important because, say the researchers, people will soon be living in space in greater numbers and it’s relatively easy to grow lettuce in hydroponic environments.
“Starting with sterilized seeds is a way to reduce risks of having microbes on plants,” said Kniel. “But then microbes may be in the space environment and can get onto plants that way.”
Wishing you clear skies and wide eyes.
